CO2 hydrogenation to light olefins on ZnO-ZrO2/SAPO-34 tandem catalysts: optimize the Zn/Zr ratio

The hydrogenation of CO2 to light olefins is a promising method for CO2 resource utilization. Tandem catalysts composed of metal oxides and zeolites have been widely studied for the hydrogenation of CO2 to light olefins, but there are bottleneck problems in terms of CO2 conversion and light olefins yield. ZnO-ZrO2 catalyst is extensively employed in CO2 hydrogenation because of its excellent stability at high temperatures, but there is still a "seesaw" problem between the CO2 conversion and light olefins selectivity. In addition, the synergetic effect between Zn and Zr sites on the reaction process remains unclear. In this work, a series of ZnO-ZrO2 catalytic materials with various Zn: Zr ratios were synthesized by co-precipitation, and the interaction between Zn and Zr could be regulated by altering the Zn: Zr ratio. XRD and TEM results confirmed the successful synthesis of ZnO-ZrO2 composite oxide and the existence of a certain interaction between Zn and Zr. CO2-TPD, H2-TPR and XPS results indicated that the interaction between Zn and Zr could improve the hydrogenation capacity of the catalyst and also induce the generation of abundant oxygen vacancies to effectively promote the adsorption and activation of CO2. Catalytic performance results showed that ZnO-ZrO2(1:4)/SAPO-34 exhibits the best CO2 to light olefins activity with a CO2 conversion rate of 26.4% and a C2=-C4=selectivity of 72.6%. This work provides a feasible strategy for rational designing and optimizing of CO2 hydrogenation catalyst.